One or more embodiments disclosed herein relate generally to whipstock systems and methods. In particular, one or more embodiments disclosed herein relate to whipstocks for sidetracking a borehole from a wellbore.
Traditionally, whipstocks have been used to drill deviated boreholes from an existing wellbore. A whipstock has a ramped surface that is set in a predetermined position to guide a drill bit or drill string in a deviated manner to drill into the side of the wellbore, which may also be called a sidetrack window or window. In operation, the whipstock is positioned/set on the bottom of the existing wellbore, the set position of the whipstock is then surveyed and the whipstock is properly oriented for directing the drill string in the proper direction. After the whipstock is set, a drill string is lowered into the well into engagement with the whipstock causing the drill string to drill a deviated borehole through a wall of the existing wellbore.
Other uses for whipstocks include sidetracking from previously drilled and cased/uncased wellbores that have become unproductive. For example, when a wellbore becomes unusable, a new borehole may be drilled in the vicinity of the existing cased or uncased wellbore or, alternatively, a new borehole may be sidetracked from the serviceable portion of the existing, cased or uncased wellbore. Sidetracking from a cased or uncased wellbore also may be useful for developing multiple production zones. This procedure can be accomplished by milling through the side of the casing and/or into the wellbore wall with a mill that is guided by a wedge or whipstock component. After a milling or drilling procedure is completed, the whipstock may be removed from the wellbore.
Cement plugs may be set in the wellbore in sidetracking operations to prevent hydrocarbons or other fluids from lower sections of the wellbore seeping up past the whipstock location. The cement plug is set below the whipstock to isolate lower sections of the wellbore. Typically, a cement plug may be set during a first trip into the wellbore, after which the whipstock may be run into the wellbore in a second trip. Accordingly, existing operations employ two or more trips downhole.